Material-handling systems transport media (envelopes, boxes, cards, sheet material including paper, corrugated cardboard, mail or the like or stacks of sheet material) from input station(s) to output station(s). A conveyor system, for example, may transport any number of media items between an inlet station(s) and a delivery station(s). Belts of the conveyor system carry stacks of media between two successive pushers (elongated members, attached to a belt at predetermined locations, separating two sections of the belt and being capable of pushing media on the conveyor system) on the conveyor system.
Pusher transport systems encounter the problem of misregistration or misalignment of media in a stack. The misregistration of a media stack can occur due to addition of media in an unregistered state to a media stack, addition of media leading to an unregistered stack, and transportation of the media stack, where movement can lead to an unregistered media stack. For example, in a mailing system where differently sized media is added to a media stack during transport, misregistration can occur. Further, the mailing system may involve inserting the media stack into an envelope, necessitating proper registration of the media stack. Presently, hold down straps and brushes placed at fixed locations above the conveyer system are employed for tamping an unregistered media stack. A change in the size or type of media causes significant delay in media transport, as an adjustment to the hold down straps or brushes becomes necessary.
It would be highly desirable to have a relatively simple and cost-effective system for combining high production on a material-handling system with the ability to vary the distance between successive pushers automatically for tamping media stacks during transport.